Polyketones, i.e., polymers having carbonyl groups incorporated in the polymer chain, are known and are most commonly produced by polymerizing carbon monoxide with one or more .alpha.-olefins. Polyketones of this type derived from ethylene and carbon monoxide are disclosed by Brubaker in U.S. Pat. No. 2,495,286. Numerous other liquid and gas phase procedures utilizing Ziegler and radical catalysts have been described in the prior art for polymerizing carbon monoxide with ethylene and other olefinically unsaturated monomers. A general review of the properties, preparations, reactions and uses of olefin-carbon monoxide copolymers can be found in the Encyclopedia of Polymer Science and Technology, Vol. 9, p. 397-402, John Wiley & Sons, Inc. (1968).
Various procedures are known for the chemical modification of polyketones. U. S. Pat. No. 2,457,271 discloses a method for modifying monoolefin-carbon monoxide copolymers to increase the degree of unsaturation by heating the copolymer in a solution of an organic solvent with a minor amount of an alkali metal hydroxide. The copolymer is reacted until the oxygen content is decreased by at least 5% or the iodine number increased to at least 25. Modification of polyketones (monoolefin-carbon monoxide copolymers) by reaction with hydrazine hydrate and related nitrogen-containing compounds is described in U.S. Pat. No. 2,457,279. A process for reacting polyketones with hydrogen cyanide to prepare polycyanohydrin resins is disclosed in U.S. Pat. No. 2,495,284.
U.S. Pat. No. 2,495,292 discloses the catalytic hydrogenation of monoolefin-carbon monoxide polymers in the presence of a nickel catalyst to reduce the carbonyl groups to secondary alcohol groups and obtain high molecular weight polyhydric alcohols. U. S. Pat. No. 2,846,406 relates to a process for reacting monoolefin-carbon monoxide copolymers with formaldehyde and specific ammonium or amine salts to produce polyamines of relatively high molecular weight. Another process for modifying monoolefin-carbon monoxide copolymers by reaction with hydrazoic acid in the presence of an acid catalyst is disclosed in U.S. Pat. No. 3,068,201.
Processes for producing thermoplastic polymers from polyketones are also disclosed in U.S. Pat. Nos. 3,979,373 and 3,979,374. The products of U.S. Pat. No. 3,979,373 are polymeric furan derivatives obtained by reacting an equimolar alternate copolymer of ethylene and carbon monoxide with a strong acid, e.g. sulfuric, phosphoric, p-toluene sulfonic, etc., at 40.degree.-200.degree. C. The polymeric pyrrollic polymers of U.S. Pat. No. 3,979,374 are obtained by reacting an equimolar alternate copolymer of ethylene and carbon monoxide with a primary monoamine in the presence of strong acid and a solvent at a temperature from 40.degree.-100.degree. C.
U.S. Pat. Nos. 4,616,072 and 4,687,805 disclose halogenating ethylene-carbon monoxide copolymers by contacting said copolymers in a liquid medium and in the presence of an anionic halogenation catalyst selected from Lewis acids and Lewis bases.
Oxidation and chain cleavage of ethylene-carbon monoxide copolymers to produce mixtures of .alpha.,.omega.-dicarboxylic acids ranging from succinic acid through dodecanedioic acid and possibly higher and their corresponding esters is disclosed in U.S. Pat. No. 2,436,269. The oxidation is typically accomplished utilizing nitric acid and a vanadium oxidation catalyst, e.g., vanadium pentoxide or ammonium vanadate. Other oxidizing agents which are disclosed include the higher oxides of nitrogen, chromic acid, permanganates, molecular oxygen or air, or mixtures thereof.
A process for converting polyketones to polyesters by oxidizing ethylene-carbon monoxide copolymers in a liquid medium using organic peroxyacid oxidizing agents is disclosed in U.S. Pat. No. 4,929,711. Substantially all or only a portion of the carbonyl functionality can be oxidized by the process. In U.S. Pat. No. 4,957,997 it is disclosed to oxidize polyketones containing pendant functionality groups, such as ethylene-vinyl acetate-carbon monoxide terpolymers, using organic peroxyacids to convert substantially all or only a portion of the carbonyl functionality to oxycarbonyl groups. European Patent Application No. 89202833.3, published Jun. 13, 1991, as Publication No. 0372602, also discloses that derivatives of polyketones can be obtained using the Baeyer-Villiger reaction. Aromatic peroxyacids are suggested as the oxidizing agent for this reaction with an acid catalyst.
While peroxyacids are effective oxidizing agents for polyketones, they are expensive and in some cases are dangerous to handle. It would be highly advantageous if a process were available whereby carbonyl groups incorporated in a polymer chain, such as with polyketones obtained by the polymerization of olefins and carbon monoxide, could be oxidized to ester groups utilizing hydrogen peroxide as the oxidizing agent. It would be even more advantageous if this could be accomplished without significant cleavage of the polymer chain, i.e., without substantially altering the molecular weight and molecular weight distribution of the polymer. Substituting hydrogen peroxide for the organic peroxyacids in the above-described processes of U.S. Pat. Nos. 4,929,711 and 4,957,997 has not, however, proved to be effective for converting carbonyl groups to oxycarbonyl moieties. The use of Lewis acids, e.g., BF.sub.3, with hydrogen peroxide, a widely used reagent combination for the Baeyer-Villiger oxidation of numerous keto compounds provides unacceptably low conversions with polyketones.
It would be highly advantageous if a process which utilized hydrogen peroxide as the oxidizing agent were available to convert carbonyl functionality present in the polymer chain of polyketones to oxycarbonyl groups. It would be even more desirable if the process could achieve conversions of 40 percent or greater with minimal production of undesirable by-products. These and other advantages are realized by the process of the present invention and will be described in more detail to follow.